[swift-evolution] [Proposal] Shorthand Argument Renaming

[Haravikk]

I agree with the intent; I don’t especially like the dollar-sign syntax either, but I’m not a fan of this as an alternative either.

Considering this is a kind of compiler magic, what about using #0, #1 etc. instead?

> On 30 May 2016, at 17:44, Frédéric Blondiau via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Hello,
> 
> I was thinking about this, and would like to get some feedback before making my first proposal.
> 
> Best regards,
> 
> 
> Fred.
> ---
> 
> Shorthand Argument Renaming
> 
> 
> Introduction
> 
> Swift automatically provides shorthand argument names to inline closures which cleverly allows us to write
> 
>    reversed = names.sort( { $0 > $1 } )
> 
> I would suggest to use another syntax, using these new “names”
> 
>    reversed = names.sort( { .0 > .1 } )
> 
> 
> Motivation
> 
> The $n notation is generally used with positional parameters using one-based numbering, $1 referring to argument 1; $2, to argument 2... with a special meaning for $0 (could be the name of the function, or the full list of parameters).
> 
> This $n notation is often handy, but feels strange in Swift... like imported from UNIX scripting (but here zero-based, anyway).
> 
> 
> Proposed solution
> 
> The .n notation is more Swift-like — as used to access Tuple members, for example.
> 
> 
> Detailed design
> 
> Today, .0 or .1 (as any .n's) are refused by the compiler, as being not valid floating point literals.
> 
> I’m not a compiler expert, but eventually fetching this error inside a closure body could easily be translated into accepting this new syntax.
> 
> There can’t be conflict with other shorthands (like accessing static members using dot notation) as members can’t consist of only digits characters.
> 
> 
> Impact on existing code
> 
> $n need to be rewritten .n
> 
> 
> Alternatives considered
> 
> Create a default argument named “arguments” (like “error” in catch, “newValue” in setters or “oldValue” in a a didSet observer) accessed like a Tuple
> 
>    reversed = names.sort( { arguments.0 > arguments.1 } )
> 
> but this is (of course) much less convenient.
> 
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